Conventional practice is to design a radio transceiver targeted to a particular standard. For example, a radio transceiver to be used in a device that operates using the Bluetooth™ communication protocol is typically sized and customized to the Bluetooth protocol. Generally the same can be said for radio transceivers designed for use in devices that operate using the IEEE 802.11 communication protocol.
Historically, a user that is interested in communicating in particular systems operates a distinct device dedicated to each of the communication protocols. The user is required to have multiple devices, with each device limited to communicating over a particular communication system using a particular communication protocol.
However, there is a trend in many applications that a communication device operates multiple communication protocol technologies, or operates multiple instances of the same communication protocol technology. Communication devices are continually shrinking in physical size and simultaneously increasing the ability to communicate over multiple communication systems each having a corresponding communication protocol. A multi-mode communication device can be configured to support communications over a Wireless Local Area Network (WLAN) as well as communications over a wide area network, such as a wireless telephone network. For example, a multi-mode communication device such as a cellular telephone device may include IEEE 802.11 WLAN and Bluetooth functionality along with GSM functionality.
The term WLAN typically refers to a class of wireless communication technology that operates at a distance up to 100 meters, and WPAN is commonly used to refer to a class of wireless communication technology that operates up to a distance of 10 meters. For simplicity, when used herein, the term WLAN is meant to encompass at least systems operating in accordance with standards such as IEEE 802.11/DS, 802.11a, 802.11b, and 802.11g. It should not be limited to these technologies as any other shorter-range wireless communication technology, particularly, but not limited to, those that do not require a license for operation by the Federal Communications Commission (FCC) in the United States (U.S.) and other similar unlicensed bands outside of the U.S.
Wireless telephone networks can operate according to a variety of communication standards and corresponding communication protocols. Wireless telephone systems include, but are not limited to, those systems operating in accordance with GSM, GPRS, EDGE, AMPS, CDMA and WCDMA standards.
While it is desirable to provide a radio transceiver system that can be used for more than one communication protocol technology, supporting multiple communication standards in a single device creates additional issues and design effects that need to be addressed. One drawback to a multi-mode device approach is that one sub-system can interfere with another sub-system since they are not synchronized to one another.
The different communication systems are rarely synchronized with one another, and can operate at different frequencies, bandwidths, and communication rates. The lack of synchronization between communication systems can create interference problems within a multi-mode communication device. For example, if a first sub-system in a multi-mode communication device transmits while a second sub-system within the multi-mode communication device attempts to receive, the first sub-system's transmission can leak into the second sub-system's receiver, thus blocking or otherwise degrading any incoming messages intended for the second sub-system.
One manner of reducing the effects of interference generated by a first sub-system on the operation of a second sub-system is to increase the isolation between the separate sub-systems. Expensive isolation techniques such as filtering can be used to improve this unsynchronized multi-mode performance. However, there are limits to the ability to isolate a first sub-system from a second sub-system integrated within a single device. The continual desire to minimize the overall device size and weight further complicates the attempts to isolate various sub-systems. It is therefore necessary to develop technologies that configure multiple transceivers within a unified multi-mode communication device such that the transceivers for the distinct communication systems minimally interfere with one another during transmission and receptions.